LCD (liquid crystal display) technology has obvious advantages, such as a low driving voltage, a low power consumption, a high reliability, a huge information-displaying amounts, a color display, a flicker-free, a low cost, a capability of being made into various sizes and types LCD displayer, a convenience of portability and so on. Because of these above advantages, LCD technology has a great influence on the product structures for imaging displays, thereby facilitating developments of microelectronics and optoelectronic information technology. With continuous development of LCD technology, the demand for liquid crystal display panels is also increasing.
The liquid crystal, which is in a state between liquid and crystalline, is the core material for LCD technology. The liquid crystal has some properties of both a liquid state and a crystalline state (such as fluidity, anisotropy, etc.), as well as its own unique properties. For example, after the power is turned on, the liquid crystal becomes orderly arranged to enable lights to pass therethrough easily, whereas after the power is turned off, the liquid crystal is arranged chaotically to prevent the lights from passing therethrough. Based on the above characteristics, a liquid crystal layer comprising liquid crystals can be made, and the liquid crystal layer is disposed inside an LCD panel. When a light beam passes through the liquid crystal layer, the liquid crystals of the liquid crystal layer become orderly arranged or chaotically arranged, according to the circumstances of the electricity passing, so as to allow lights to pass therethrough or block the lights and then display the corresponding images. Therefore, an outstanding image definition greatly depends on the merits or demerits of the liquid crystal characteristics.
In a case of a moisture content ratio for the liquid crystals, during an actual production process, the moisture content ratio in the liquid crystal material has a higher requirement. Generally, the moisture content ratio has a requirement of less than 10 ppm (parts per million concentration). A higher moisture content ratio will reduce the impedances of the liquid crystals, thereby lowering a voltage holding ratio of the liquid crystal panel which would invoke an image defect such as an IS (Image Sticking). Therefore, the measurement and control of the moisture content ratio in the liquid crystals brings a significant effect on the LCD technology.
In prior art, a primary method of measuring the moisture content ratio of the liquid crystals is ‘Karl-Fischer’ method (referred to as KF), which mainly applies a Karl-Fisher reagent on a liquid crystal sample to measure its moisture content ratio, wherein the Karl-Fisher reagent includes SO2, I2, organic alkali and an alcohol solvent. The measurement principle of the Karl-Fischer method is given in the following formulas:I2+SO2+2H2O→2HI+H2SO4  (1)C5H5N+H2O+I2+SO2→2C5H5N.HI+C5H5N.SO3  (2)C5H5N.SO3+CH3OH (anhydrous)→(C5H5+H)O—SO2.OCH3  (3)
In which SO2 and I2 are oxidation-reduction reactions with the moistures of the liquid crystal sample, quantitatively. The chemical relationship is a quantitative basis of the moistures in the sample. The organic base is mostly pyridine, which is used to neutralize the acid generated during the reaction and to perform the reaction toward a right direction. The alcohols, mostly methanol, are mainly used to react with the unstable sulfuric anhydride pyridine generated in the reaction, and to form a stable Methyl sulfate pyridine, treated as a reaction medium.
Please refer to FIG. 1. A liquid crystal sample with a quantitative amount is drawn by a syringe to infuse into the Karl-Fisher cuvette containing the Karl-Fisher reagent for directly conducting the reaction, the end of which is indicated and monitored through a double-platinum indicator electrode within an instrument. However, in the research process the inventor of the present invention found that the liquid crystals mostly contain some substances with low polarity, such as a benzene ring or cyclohexane, which are not compatible with the methanol system with medium polarity of the Karl-Fisher reagent and easily exist in the form of dough insolubles that are not beneficial to release and test the moistures in the liquid crystals. This greatly reduces the accuracy of the test of the moisture contents in the liquid crystals. With the lower moisture content of the liquid crystal sample, it's difficult to release trace of the moistures wrapped in the liquid crystals, which easily results in moisture content measurement errors. This will eventually lead to adverse LCD panel displays after the formation of a liquid crystal panel.
Therefore, there is a need to solve the above problems of the prior art.